Study On The Heavy Metal Wastewater Treatment By Loading Flocculation Sedimentation Process

Coagulation precipitation technology, which occupies a critically important position in themodern water treatment process, has greatly important influence on the subsequent process, andthe effect of Coagulation precipitation directly affects the quality of final effluent water andoperation cost. Therefore, how to improve the effect of solid-liquid separation in coagulationprecipitation technology to achieve the efficient effect of flocculation clarifying, has been animportant field in water treatment all of this days. The loading flocculation process is ainnovative and efficient solid-liquid separation technology for nearly a decade, which isdeveloped and explored based on the contact flocculation and accelerated clarificationtechnology by adding the appropriate amount of coagulant to form the larger and the morecompact flocs by condensation of collision by trapping and sweeping the flocculation particles inthe water for mixing, to greatly improve the effect of flocculation to achieve high efficientsolid-liquid separation. The advantages of this process were: high efficiency of clarification,strong ability of anti-shock, stable effluent quality, save land area, etc.The comparative test and orthogonal test were used in this research to study the optimaloperation condition of the loading flocculation process and conventional flocculation process andthe treatment effect were compared. The main contents of this test were:the pH value, thedosage of coagulant, the dosage of aid coagulant, the precipitation time, the sludge recirculation,the effect of hydraulic loading conditions on the flocculation effect of flocculation process andthe comparison with different coagulants. The best operation parameters of pilot test was used tobe as reference, a pilot scale test about flocculation orthogonal load was done with the pH valueof the mixture and the flocculating constituent, the dosage of ferric chloride,the dosage of PAM,the sludge recirculation for influencing factors,to got the optimum operation conditionparameters, in order to provided the reasonable process parameters for practical production.Based on PAC as the coagulant,when the pH is9-11, PAC dosage is10-5mg/L and thecoagulant dosage is0.5-1mg/L,the loading flocculation process was well capable of dealing withthe zinc. As for the copper,however, the pH10-12, the coagulant10-15mg/L, the PAM dosage0.5-1mg/L,its performance was also fairly good.When the pH is10-11, the coagulant dosage is5-10mg/Land the PAM dosage is1-2mg/L,the zinc is efficently removed by the loading flocculation process on the basis of aluminum sulfate as the coagulant. AS always, the pH11-12,the coagulant5-10mg/L, the PAM dosage1-2mg/L,the loading flocculation of copper removaleffect was pretty well.Both of the coagulant’s flocculation effect was best when the settling timeis10mins, backflow sludge quantity4000-5000mg/L.The results showed ferric chlorideflocculation effect was best after a comparative test for aluminum sulfate、PAC、PFS and ferricchloride as the coagulant was made.By Orthogonal test,the best hydraulic conditions were fastmixing speed,300r/min, fast mixing time,80s, slow stirring speed,50r/min, slow stirring time,4min.the flocculation’s optimal processing parameters of the loading flocculation process wereblend pH11, flocculation pH8.5, ferric chloride dosing15mg/L, PAM dosing1.5mg/L,backflow sludge quantity4000mg/L.when disposing wastewater containing zinc, copper as rawwater.Compared with the conventional flocculation process disposing heavy metal wastewater,loading flocculation technology has many major advantages,for instance, the pH changeadaptability is stronger, quantity of reagent is less, the removal efficiency of heavy metal isbetter, the settling velocity of sludge is faster, the ability of anti-shock loading is stronger, theeffluent water quality is more stable,so it can effectively promote the flocculating effect, shortenthe flocculation time and save the operation cost. This technology not only has prompted thecoagulation sedimentation process to be good progress, but also brought good social andeconomic benefits.